Electrode holder assemblies are often seen in chemical laboratories and other locations where it is necessary to perform either qualitative or quantitative analyses on various sample solutions or substances. The assemblies are used to support one or more test probes or electrodes that are immersed in a sample of a substance in order to obtain a desired analytic test parameter from the substance. An example of such probes is a pH meter test electrode that is used to find the H+ ion concentration of a sample.
In most test situations it is necessary to make measurements of a large number of sample solutions. This necessitates repeatedly inserting a test electrode into a sample container, taking a measurement, removing the electrode, and inserting it into the next container of sample solution.
Currently, there are three types of electrode holder assemblies in general use: platform holders having platforms adjustably mounted on vertical support rods, holders that are supported directly on the sample containers; and platform holders attached to articulated arms. None of these designs provides for simple vertical movement of the test electrodes so that they can be inserted and removed from the sample containers with only minimal effort.
Electrode holders attached to vertical support rods are a very common type of test probe support. These assemblies comprise a vertical support rod secured to a base, a platform adjustably supported on the rod by a thumb-screw clamp and in turn carrying the test electrodes. To raise and lower the platform it is necessary to turn the thumb screw to release the clamp, move the platform to the new height, and reset the thumb screw. When test electrodes are attached to the platform, the operator must use extra care to insure that when the platform clamp is loosened, the platform does not fall. This usually requires the use of two hands to adjust the position of the electrodes, one to manipulate the clamp, and the other to support the platform when it is nonclamped from the support rod. If the test probes are being used to test a succession of samples, the operator must spend considerable time manipulating the clamp and raising and lowering the platform so the successive sample containers can be placed underneath the platform.
A platform holder is a platform, with proberestraining bores through which test probes are inserted. The platform is placed over a sample container so that it rests directly on the rim of the container. To perform analyses on successive samples it is necessary to lift the platform with the probes from the first sample container, place the next sample container within reach of the platform and place the platform on the second sample container. Since the probes are often fragile, it is generally necessary to hold the platform while changing sample containers so as to prevent the electrodes from striking a hard surface and being damaged.
Articulated arms have been provided for the raising and lowering of electrodes. These arms, usually having one or two rods hinged with an electrode platform pivotally attached to the end of one rod so as continually to be horizontally aligned, have their own disadvantages.
To provide an arm with a sufficient range of motion, and yet maintain sufficient stability, the base must be large. Moreover, in a laboratory, where it is desirable to have all necessary equipment close at hand, and where space may be at a premium, working around such an arm may be difficult.
A need therefore exists for an electrode holder assembly that allows test electrodes to be accurately positioned in and removed from a sample container with minimal effort and without interfering with other equipment or other tasks being performed by the operator.